Building a slot processor

[bmac]

I've been toying with the idea of building a slot processor for my darkroom. I figure I can make it out of plextglass and use small plumbing fixtures to drain it when I was done. I wouldn't really need any heating, due to only working with black and white. I don't understand why the Nova's are so expensive. Am I missing something?

 

[Les McLean]

The Nova slot processor is quite basic in construction but is totally hand made so part of the high cost is down to labour. I think we also have to pay a premium for the original idea. Before the Nova hit the market the only mechanised processors available were extremely expensive. I know of many photographers in the UK who have attempted to build a slot processor because they thought it would be a simple job, I've yet to see a success. I'm not saying that you can't do it Brian, if you are a good DIY'er it is possible but there are many people around like me who cannot cut a piece of wood straight and square. I also believe that plexiglass (perspex in the UK) can be difficult to cut. Best wishes with the project and please keep us posted on the progress.

 

[Annemarieke]

I thought the Nova washer was made of glass? Wouldn't it be possible somehow to use glass in stead of plexiglass? I have been toying with the idea too for a while, after having used a Nova washer in somebody else's darkroom. They are great, especially if you do a lot of fibre printing and need very long washing times. I do agree with Les that the Nova is worth the money, but it is still a lot of cash...

 

[docholliday]

I built a slot processor a while back before going to an autolab and a CAP-40. Cost me about $45.00. Here's how to do it easily:

1) get a glass aquarium tank, around 10-20 gallons (the square kind) or whatever size you want for the prints you're working on. (Now, if somebody does this with a 300 gallon, you're braver than I am...)

2) have 3 pieces of plexi cut that fits the tank, width-wise. These are the "tank" dividers. I used the white, translucent kind. I had a long side "rounded" with sandpaper so I could drag prints against it. You can have these sheets cut at Lowe's or any home improvement store. Alternatively, you can go to a glass shop and get some glass cut and the corner's rounded (I have some of these sheets done for contact printing).

3) have 2 pieces of plexi cut that fit against the left and right wall and another piece cut to fit perfectly in the bottom of the tank. Have these three pieces scored (I did mine with a router) the depth of the pieces from #2 (depth meaning the thickness)

4) put the last piece from #3 in the bottom of the tank, then the other 2 pieces from #3 against the sides. Now, slip the 3 from #2 into the grooves you cut and be sure that all seats well.

5) use EPOXY, not, I repeat, NOT silicone sealant to glue these together once everything fits. Be sure everything "locks" into place first, then fill the grooves on the bottom piece first. I actually assembled the "insert" outside of the tank and dropped it in (I had to rip the black plastic "rim" off the tank, but reglued it later.).

6) when the epoxy is dry, fill slot #1 with water and see if it leaks into 2, if it does, drain the tank, dry it out, and use a chopstick to put some more epoxy where the leak occurred (you'll see it in then next tank if you shine some light into the neighboring tank). Once you've tested all 4 tanks, let the whole unit dry overnight and check again.

7) using the protective bags from 11x14 or 16x20 paper, wrap the outside of the tank, cut to size, and glue to the glass with spray adhesive such as 3M Super 77.

8) at the hardware again, get some pipe which will fit almost into the slot, but not fall in cut the width of the tank. These are your "floating covers". I had the ends of mine plugged with rubber corks for larger flasks. You can also lay the end of the pipe against wax paper and pour epoxy into the pipe. Then, drill a small hole in the middle of the pipe, flip around and inject more epoxy on wax paper to fill the other end. Then, a touch of epoxy to fill the "filler" hole.

The biggest pain was getting the chems out of the slots, so instead of putting drain valves in (it's more of a pain to seal stopcocks into glass), I used one of the battery operated kerosene pumps to suck the chems out. You could always use the gravity method with a squeeze bulb type.

To clean out the slots, I used some processor cleaner and a baby bottle brush.

Worked great for RA-4 and B&W. Then, I got the roller transport and hand developing disappeared from my darkroom...(except for fiber B&W, which is still in tray).

 

[Donald Miller]

If I were building one, I would build it out of acrylic only. Using acrylic throughout would facilitate the joining of materials. I have worked with acrylic and it cuts quite readily with a table saw. It glues together very well with acrylic cements and these are much more positive then trying to join acrylic to glass by either epoxy of silicone. The reason that they are more positive is that they work through a "wicking" action and actually melt the surface acrylic of the two surfaces being joined. It is more correctly identified as a chemical welding.

I would think that you would have an acrylic supplier/fabricator where you live Bryan. We have two, of which I am aware, in Wichita and your city is of considerably greater size. The reason that I mention this, is the acrylic supplier/fabricator would be able to give the slight bend to the upper portion of the dividers (as does the Nova). This would facilitate the loading and unloading of prints. I have not attempted bending acrylic but I imagine that it does require heating the material.

The drain problems are eliminated through using acrylic since it drills and taps quite readily. This would allow one to obtain drain fittings and screw them into the respective compartments.

The temperature control could be accomlished by using a heated tempering bath as a supplemental compartment beneath the chemical compartments. WW Grainger has cartridge type heaters which I have used for my tempering bath and they also have temperature controllers which are solid state and quite accurate.

 

[DKT]

Sintra might be another good material to try. It's compressed PVC sold in a sheet like plywood and can be glued, drilled, cut on table saws, routed, painted, etc--just like wood. It's water proof and comes in a variety of thicknesses and colors. You can heat form it too---150 degrees or something is the temp for that kind of work...we use it in our exhibit shop... It's kinda expensive though, a 4x8 sheet is about 80+ bucks...It would be really easy to work with though...I made a lensboard out of a scrap of black sintra using a dremel even....

here's a link, you can get the tech specs off this:

http://www.alcancompositesusa.com/sintra_bio.html

btw--you could configure it with simple gravity fed hoses to get the chem out. Since it's PVC, drill the hole for a PVC fitting even and use some of that cement they sell for plumbing to bond it in there--for tempering, you could use immerison heaters, probably what I'd do would be to use a thinner material for the slots, and build a waterjacketed tank to hold them in....you could put an immersion heater in this, and use recirculated water through a little pump in this bigger tank..like a phototherm unit.

 

[Aggie]

..

 

[kenh]

I have built a processor out of plexiglass and glue. Actually, since I used plexiglass that was too thin I was able to just score it with a knife and break it carefully. The completed unit took just a few evenings to make. Although the unit looks scarry when loaded with over 5L of liquid and the sides buldging.

Problems to think about are:
1) the clips to hold the print and move it along
2) How to prevent the print from sticking to the plexiglass

I use lighting pannels from floursecnt light fixtures inserted into the tank to prevent the print from sticking to the plexiglass.

I made some clips with some nails, glue, and some inexpensive plastic clips.

Ken

 

[Justin Low]

I'm planning to build my own in the coming weeks. I intend to use acrylic sheets (either 1/4" or 1/8" thickness) and join them using chloroform. I shall be building one to take 8x10" sheets of RC B&W paper, and I'm trying to keep the amount of solution required to 1 liter per slot (3 slots, one each for developer, water stop, and fixer). I might have to reinforce the joints with a sillicon sealant but I'm not sure about that at this point.

Will keep everyone updated.

 

[bmac]

How do you intend to keep the prints from sticking to the sides? I actrually gave up on trying to build one, and bought a Nova, the nsold the nova because it cramped my work style.

bmac - back to trays

 

[Justin Low]

Unfortunately, I'm on a student's budget (cheap!) so I won't have the luxury of buying a Nova, nor do I have the luxury of space to use a set of trays. So...

I don't intend to stop them sticking. I'm actually intending for them to stick. As I'm using RC, the chemistry does not soak into the base, but just reacts with the emulsion surface. So as long as the base-side sticks to a panel, there is no problem. If one side is stuck, then naturally the other side should not be.

If I need to get a non-stick surface, Ken's point about the lighting panels for flourescent lights should do the trick.

I will build a prototype with vertical walls first, rather than slanted walls, to see if it works well for me. I might build one with slanted walls at a later stage should I need a bigger processor.

I did the calculations, a slot that is sized 300x250x15mm should hold 1 liter of chemistry comfortably, with a little room at the top.

Sorry to bring this thread back after over a year.

 

[Aggie]

Why not a tray ladder? it is cheaper and keeps the trays stacked so you save space. Ann knows where to get them. It would probably be a whole lot less expensive than all the plexiglass and the headache of working with it.

 

[Justin Low]

That's true about the cost Aggie, however, I'd have to spend a lot of time setting up the chemicals every time I want to print and spend more time pouring it away. In a slot processor, I believe the chemicals should not detoriate as fast due to exposure to air as the exposed surface area is minimal.

I don't intend to use plexiglass as it's hard to work with and it's expensive (as you say). Acrylic is cheaper, easier to work with and if it's good enough for Nova, it should be good enough for me.

I'm a little worried about sludge buildup, but I think I can deal with that at a later stage.

 

[L Gebhardt]

I made a set of them out of plexiglass. Actually I should say I had the plastics shop make them. Once I figured out the materials cost their labor was almost free. Mine are about 12.5x15.5 inside dimensions and about 1 inch across for each slot. They hold about 3 liters each. Over time the sides have started bowing on the outer tanks (I keep them all strapped together) even though they are made from 1/4 inch plexi. I used the Nova clips to hold the paper. Sometimes the paper sticks to the smooth side, but not badly. The biggest problem is the developers leave deposits on the sides which require frequent cleanings or you get stains on the print edges (I never had it stain the image area for some reason).

If you are short on space a set of three 8x10 tanks should cost under $100 to have built and be easy to use. I would still use a 1 inch wide slot so the clip and print have room, even though this will take you up to about 1.8 liters per tank.

 

[rjr]

Justin,

when I bought my Jobo Prima the Dev and Fix troughs were filled with silver sludge. The Jobo has a textured structure to prevent uneven development by sticking paper on the walls, making a buildup of sludge easy.

I got rid of it by using slightly hot Blix, bleachfix, leaving it in it overnight... the fix tank is very clean now, the dev tray needs a third pass.

 

[John McCallum]

Brian, how did the slot processor cramp your style? Was it print sizes that were the problem?

cheer, john

 

[bmac]

found it ok for proofs, but not ideal if you want to watch the print develop, ans the action required for constant agitation made my wrist sore after a while.

 

[John McCallum]

Your comments are interesting. I've been wondering if a slot processor might be the way to go for printing higher numbers. That is, once you have the print looking how you wish, and (perhaps in a fleeting moment of optimism) it's time to bang out 10-12 copies.
Any thoughts?

 

[bmac]

I think any speed gained by using verticle slots would be lost by having to wash / dry the clips between every print.

 

[John McCallum]

Thanks muchly, good to know your thoughts.

 

[L Gebhardt]

I never dried my clips, just a quick rinse was all I found necessary. I also found it easy enough to agitate - I just slid the clips back and forth along the top of the slot. The reason I stopped using mine was that I felt it was wastefull because I needed to mix up a lot of chemicals to fill the slots, and frequently I didn't use them up. I still pull them out if I want to print 11x14's as my tray space is limited.

 

[JD Morgan]

So why do they not use a carrier rack in the slot?

You know, an assembly that is very perforated with cut grooves on each side that the paper would slide in (like a 4x5 combi-tank). With multiple paper grooves an 1/8" apart you could get maybe 6 prints in a carrier designed for a one inch slot.

An auto-agitator would be relatively simple to construct for something like that.

Just like makin' french fries.